Operation procedure for gas lifts



1953 w. w. WEINRICH 2,649,340

OPERATIQN PROCEDURE FOR GAS LIFTS Filed June 14, 1950 INVENTQR Ulflham ULUhuNRmH aw mww ATTORNEY Patented Aug. 18, 1953 Uni-ED i LIFT t6, Houdry, Process Corporation, Wilmington,

ew e rre eiiene nelewete Application June 14, 1950, S e rial; iofliiisf (01.302463 This inventicn relates ingeneral to cyc 1c U k version systems in Whichsolid contactmateria 5; pa sed; by -e o ne do -flair hat wherein the material is contacted by gaseous-zige et i an e ated the s r i ac n along-lap up-iiow path In pa ticular; the inven-z tion relates tothosecyclic conv sion system in which ,the, aforementionedelevation -=of contact material is inflected hy tengaging. the-.- material; Within" wa es ab shed absin h lsweweee end of the lift path: with lift -gas-introduced in o, the engaging gone in plurality of streams one oi which contains the major portion of the litt as and functions primarily as the; liftmedium, n e e n irwhichiwma n' am nes e tion of thetotal lift gas, 'nsuificientin quantitygtq alone .efie t'ih esireMif ne, hu i n tieniae r ma l a t me n fql mfldiu ei flC trolling the flow rateofithe oontactmaterial; Th emethodpf the inventionrnay, tonexampleghe ape; lied; to; the rsystem disclosed in -my -cop en 5 application -.Seria 1 1310.; 147,1 26. fi1ed jointly;with J hn V-W DeIaplaine on1March -1, wea on (em-,- bodiment of-whichdisclosesthe; elevation 0:590 tact material-in the iolloyvingmannepz- At the: r1 a o th dewnefiow the e i ctmew ri l risint i ds ed n o; i mn a n ne su e d n t e o e esd efhe i t at endi r v e oyercomeethe D ES 8 1 5.011:

. playing anwauxiliarsar e s e fie p v e system and minimize 1} S y savailableefor .e. ii aene aii mi ut m st f di a; being tQOrSlGW or. of ermitting :theeaacumulation; of substantial an i i s :Q esm a tmateriali i hedift p pea introductiomchamhenafter thefiewt- "lift-gas has ea ed, he easel when the -tota lift 382151 1313 hut hi hem yw req e uh n r t i as e si p es re -e s ab y m excess-w oehe mafimumi i S'%.1P T 5$ i rm y necessaries for; catal st Litpurposes sin order; to v n the; tatie'bed -ofa cum ates sqlita trsm a -Iw th l t Ba al "topera e i euld no rbei esi ed Without either; withdrawing a -portien of thea corrtact ma:- teri-al-zirom the introduxitf hamber, o reemaseur either-- of whichaiven esents additional expense and operatingtdifiiculty', e

l xv H v i 'fi R 2 31 invfin enwe' s rimary liftgas stream for purposesmf previdmgst'he major zl-iftingforce and asseconda r aszrstre mirunet inec i a y as arprocessicontro am nimii er tim a d: suit y se ditio d restartingebyth @Derationsiofi first, shuttingpfi:

Mites. er n as a om a t r ne dlar vq qit iee the'fiowiof proc ss: controleasiintei h en gin lower p rti of he lift patht-liftgas ptro: zone, vso. as i to,.:duick1y reduceyiboththe za't wofx duced intothe engagin @One e ngage e; c0nsolids flow into the lift -pipe ta d the lift-pressure st terial andic nve the 553 61 1 :e n inm t w d y hr ueht e .l ft.;path.-the.a 3 3: portion of the lift gas being introducedint the engagin zone in V astream discharging a o the. ower pe pher of the liftp t minor p rtion there f 7 be ns:,..:i duced; s m w ch. passes up ardlyzfromthe low region of the engagingzone through at least a portion of the moving bed;

Specifically the invention is directed tor cedures for interrupting andzrestarting the opera 5 tion of the. lift .While. shuttin down orlst rtin i up such systems, and hasflfor itsgprirnarwobiectg the provision of a j sequence. ofg-operationsmby which the flow. of :lift gas and contactv material; may be stopped and subsequently restarted With's; out adverse affectuponthe operation ofgthe. system as a whole or uponthe utilityrequirements for bringing the lift up to its normal-com; ditions. of operation. In the operationof' such.v systemsi periodic shut-downs for various-knownreasonsare anticipated, anditis-therefore-essential to. adoptthose---procedures in--shuttingdown and starting up which will impose a mini drop torrelativtely smallgszaluesand, second-shutting :off. theifiow of primary lift. gas iinto theaen 1 gaging -zone to.-interrupt solids- W} entirely; Whemthe primary stream of lift: gas' is shutioff the c ntactn aterial ceases to circulate and the small quantityf-contact materiahw-ithin the lift 7 pipe which is;;unable 'to' 'cornplete'; its travel upwe rdly through the entirefl fi, ath settles-backtrodu ction chamber Lor in l some atic dayer oftn aterial in; the bottom.

of the intro duction chamber. li-y shutting-down iftee era eni ithe s ots man er wsub start-up may read bes,- fi qt .d,=rs mply y: r

versingthe;pres:edurelandsintrodueing the ,l-primary-stream-ofditt gaszi-nto the;enga ging Z'QIlBgtQ'.

clear toutntheislight solids iaccnmul-a-ticn and 'tostart circulation dfithfl'g contact smaterial Whenthe: icirculati'o-n abecomesitstea'dy; they, secondary stream or streams of lift gas may be introduced nd. the bot-3 3 to bring the circulation rate up to the desired value.

The foregoing procedure with respect to shutting down the lift accomplishes merely an interruption of solids and gas flow, but such interruption is effected with a minimum of time loss. For this reason, it is especially advantageous when, for any reason, it is urgent to quickly stop the lift operation.

In the normal operation of conversion systems of the type referred to herein, however, there may exist various reasons for shutting down the system and interrupting circulation of contact material, such as the need for inspection or repair of the introduction chamber or of any portion of the treating equipment located in the downfiow path. In such cases, it is necessary to cut off the flow of contact material atsome point in the downfiow path above the point at which inspection or repair is to be effected. Suitable points for cutting off contact material flow, for example, may be found in the feed line or seal le connecting the lowermost treating zone in the downfiow path with the introduction chamber, in the seal leg connecting any adjacent treatin zones in the downflow path, or in the feed line or seal leg through which the contact material initially passes at the start of its downward flow. Flow control valves of conventional type are usually available at these points. To permit withdrawal of contact material from the circulatory system it is conventional practice to provide storage facilities for the same at a point of elevation in the system from which the contact material may be passed by gravity flow back into:

the circulatory path. If the object in interrupting lift operation is to drain a portion of the system, the flow control valve nearest above said portion is shut off, either'before or after the stream of secondary lift gas is shut off. At the same time, the valve which controls solids flow into storage is opened, so that the solids may pass from the upper end of the lift path into a storage vessel, and the lift operation is continued until the level of contact material in the downflow path below the point of interrupted solids flow has fallen sufiiciently to clear that portion of the system to which access is desired. If process control gas has first been cut off, such solids evacuation will naturally proceed at a rate lower than the circulation rate at which the lift had previously been operating.

In addition to the foregoing procedures for efiecting a sudden shut-down of the lift, and for effecting a shut-down coincident with drainage of contact material from a portion of the system, there is an additional procedure for shuttin down the lift system. If the circulation of contact material is to be interrupted without removing any substantial quantity of contact material from the circulatory system and there is no necessity forhaste, a shut-down of the lift may be effected by shutting ofi" first the supply of process control gas to quickly reduce the solids flow rate in the lift pipe to a relatively low value; second, shutting off the valve in the solids inlet line; and third, gradually shutting off the supply of primary lift gas. a

Each of the procedures described herein may" effect a shut-down of the system with a minimum of residual or settled contact material in the lift pipe. In any case, however, provided sufficient time is available, the lift may be cleared of substantially all solids prior down merely by slowly closing the valve controlto complete shutling the flow of primary lift gas after the secondary gas has been shut off.

For a fuller understanding of the invention, reference may be had to the accompanying drawing, forming a part of this application, which diagrammatically illustrates a typical hydrocarbon conversion unit and includes a gas lift to which the shut-down procedure of the present invention may be applied. Since the system illustrated is a typical hydrocarbon conversion system, such as a catalytic cracking unit, the contact material is a catalyst, and will hereinafter be referred to as such.

In the drawing, the conversion unit embodies a circulatory system for catalyst which may be in the form of pellets or granules having a particle size in the order of about 0.05 to 0.5 of an inch, or having, for example, an average particle size in the order of 14 mesh or larger. The circulatory system comprises separate down-flow and up-flow paths, generally indicated by the numerals I I and I2, respectively. The catalyst continuously circulates through the system, while undergoing contact with gaseous reactants or separation from gaseous products of reaction in the down-flow path, and being elevated by entrainment in a gaseous lift medium in the upfiow path. A second down-flow path, generally indicated by the numeral I3, includes storage facilities for contact material which may temporarily be withdrawn from the circulatory system. The flow paths II, I2 and I3 terminate in an upper lift hopper I4 and a lower lift hopper I5.

The catalyst is maintained as a compact moving bed I6 in the upper lift hopper I4, and is continuously supplied to the bed from the up-fiow path or lift pipe I2. The catalyst is continuously withdrawn from bed I6 and passed as a downwardly moving column through a seal leg ll, controlled by valve I8, into the upper end of a reaction chamber I9. Within the reaction chamber I9, the catalyst is successively contacted under reaction conditions with vaporous hydrocarbons in order to carry out the desired hydrocarbon conversion, and is then purged of the gaseous products of reaction before discharging from the lower end of the reaction chamber into the seal leg 2I. In passing through the reaction chamber the catalyst continuously gravitates as a compact non-turbulent bed.

The purged catalyst discharging from the lower end of reaction chamber I9 passes downwardly throughseal leg 2 I, controlled by valve 22, and is introduced into the upper end of a kiln or regenerator 23. In a well-known manner, the contaminated catalystisreactivated in the kiln by contact-with a combustion-supporting gas, such as air, which burns off the carbonaceous deposit on the catalyst. The reactivated catalyst discharges from the lowerend of regenerator 23 and passes as a downwardly moving column through seal leg 24, controlled by valve 25 into the lower lift hopper I5, the latter being the introduction chamber for the lift system.

Since a detailed description of the reactor I8 andthe regenerator 23 are not considered essentialv for an understanding of this invention,

the following brief description is believed Sllfi'lcient. The hydrocarbon vapors may be introduced into the reaction zone I9, through inlet 26 in the upper region thereof, and the gaseous reaction products may be withdrawn therefrom through outlet 21, the fiowof catalyst and gaseous material being concurrent. Purging gas,

such as steam, may be introduced through inlet 28 into the lower regionof reactionchamber 9 for countercurrent flow with respect to the downwardly moving catalyst, and the purged hydrocarbon vapors may be withdrawn from the reaction "zone through the outlet'fli.

Seal gas, for the purpose of preventing the passage of hydrocarbon gases from the reaction zone It into the upper lift hopper I4, may be supplied to the upper region of chamber ill through seal gas inlet .29.

In connection with the regenerator 23, the air or other combustion-supporting gas may be introduced through inlet 3!, and the gaseous products of combustion, or flue gas, may be withdrawn through outlet 32. Sealing gas, to prevent intermixing of the reactor and regenerator gases, may be supplied to the upper region of chamber 23 through seal gas inlet 33.

Within the lower lift hopper or introduction chamber I5 the catalyst gravitates as a compact downwardly moving bed 34. The lower end of the lift pipe or up-rflow path 12 projects centrally into the introduction chamber [5 and terminates in the lower region thereof, below the level of the catalyst bed 34. The lower end of the lift pipe is surrounded by a concentric sleeve 35 radially spaced from the lift pipe so as to provide an annular path 35 extending vertically from a point within the bed adjacent the lower end of the lift pipe to a point in the catalyst-free upper region of the introduction chamber, above the level of the moving bed. The sleeve 35 is suspended from a fixed collar frame 37 attached to the lift pipe l2 at a point above the. introduction chamber by means of adjustable link member 33 extending downwardly through slip joints 39 in the upper head of the introduction chamber.

In the embodiment illustrated, lift gas is introduced into the introduction chamber I5 at two points, one within the catalyst-free space M in the upper region of the chamber, and the other within the catalyst bed 34 below the lower end of the lift pipe [2. The major portion of the total lift gas, which may be called primary gas, is introduced above the bed 34 through inlet line 42, controlled by valve 43. Substantially all of this gas passes downwardly through passage 35. The minor portion of the lift gas, which may be called secondary or diffuser gas, is introduced into the bed at through inlet line l l, controlled by valve 65. The primary gas, which provides the major lifting effect, and the secondary or diffuser gas, which is intended primarily for control purposes, may be the same gas or different gases. In any case, it is contemplated that the secondary or diffuser gas shall be in such minor amount, up to about 35% by volume of the total lift gas, as to be insufficient alone to effect the desired lifting. If both gases are to be the same, the secondary stream may comprise a portion of the stream supplied through line :32, which portion may be by-passed through line it under the control of valve 41. With the latter arrangement, the total supply of lift gas may readily be held constant while the proportion of primary and secondary gases may be varied. The system is not necessarily restricted to the use of any particular gases for lifting purposes, but there is an obvious limitation that there be no undesirable mixing of incompatible gases in the system.

The downfiow path it is provided for hot catalyst storage during periods in which there has 6 been a withdrawal of all or .a part of the catalyst in the circulatory system. To effect such withdrawal, the catalyst in bed It of the upper lift hopper I4 is continuously withdrawn through line 48, controlled by valve .49, and passed into storage hopper 51. If valve H3 in theseal le H is shut ofi, and the lift operation continued, substantially all the catalyst in the downflow path H will be drained therefrom and passed tothe storage hopper. Obviously, an interruption of catalyst flow at any intermediate point in the downflow path will cause only the catalyst below that point to be drained and passed .to storage.

When lift operation is to be restarted, the stored. catalyst in hopper'iil is returned to the circulatory system by being passed through conmm 52, controlled byvalve 53, into the upper end of lower lift hopper l5.

In restarting after an emergency shut-down, the operations are reversed. The various control valves in the down-flow path H are opened and the valve controlling primary gas introduction is opened to, permit the flow of sleeve air through the annular passage 36. The valve 49 at the upper end of down-flow path !3 is closed, and valve 53 at its lower end is opened to permit stored catalyst to flow into the lower lift, hopper. When the catalyst flow effected by the primary gas has become uniform, the valve controlling the flow of diffusergasthrough inlet line 44 is opened and the flow of diffuser gas is regulated to bring the catalyst circulation rate up to the desired value.

To illustrate the results obtainable by the procedure of this invention, reference may be had to the following example of the operation of a 12-inch lii't pipe, using air as the lifting medium, before and after the supply of diffuser air 35 6. .1 1

Example Before After Total Air Rate (S. O. F. M.) 2,710 2,250 Percent of Total Air to Diffuser... l7 0 Catalyst Bate (Tons/hr.) -95 13. 3 Introduction Chamber Pressure (p. s. i. l 4. 5-5.0 1.2-1.4

When the lift had attained equilibrium at the after operating conditions, as indicated by a substantially constant pressure drop, the primary or sleeve gas was shut off, thus interrupting the upward flow of catalyst and reducing the pressure drop to zero. To resume operation, the sleeve air was set to substantially its previous value, and the unit was again permitted to come to equilibrium. Then diffuser air was slowly added until the desired catalyst rate was reached- For the conditions existing in the after column of the above table, the lift pressure drop when restarting the lift in this manner varied between 1.0 and 1.9 p. s. i. g. until the air and catalyst flows were established. Then the lift P essure drop returned to its former value between 1.2 and 1.4 p. s. i. g. It was thus clearly demonstrated that lift operation could be easily restored to normal without supplying lift gas in excess of the total lift gas requirement for normal operation.

Applying the preferred procedure to a typical lift system, for example, one in which the lift height is feet, the lift diameter is 12 inches, and the sleeve height, as defined in the aforementioned copending application, is such as to produce a lift pressure drop of about 0.1 to .0

p. s. i. g. when diffuser air is shut off, the catalyst circulation would range from less than tons/hour to nearly 100 tons/hour. With the diffuser air turned on in normal operation, the lift pressure drop would increase to a range of about 1.0 to about 12 p. s. i. g., and the range of catalyst circulation rates would increase to -270 tons/hour.

While the procedure for shutting-down and starting-up the lift has been described particularly in connection with the lift introduction chamber illustrated in the drawing, it is to be understood that it is not so limited. The procedure may be applied with equal advantage to any lift inlet system embodying an introduction chamber into which lift gas is introduced in separate streams, one of which introduces lift gas in major proportion to effect the desired lifting, and. the other of which introduces a minor amount of additional lift gas primarily for control purposes. Regardless of how engagement between the particles of catalyst and the lift gas is effected, a rapid shut-down of lift operation is obtained in accordance with the present invention by first reducing the catalyst circulation to the minimum value obtainable by elimination of secondary or process control gas, and then cutting off the flow of primary gas. The latter operation being timed to permit the lift to evacuate the desired amount of catalyst from the lower lift hopper, or to drain the necessary amount of catalyst from down-flow path ll.

The foregoing procedure provides a simple, efficient method for shutting down a gas lift of the character herein described by which there may be accomplished first, a substantially immediate evacuation of the major portion of the solids passing through the lift pipe accompanied by a considerable reduction in the solids concentration and solids flow rate therein and, second, an interruption of the solids flow at a time when there is a minimum of solids within the lift pipe which may settle at the bottom thereof when the flow of gas has ceased. 7

Although in most instances, it may be preferred to gradually shut off the flow of primary gas in order that there may be almost complete evacuation of the lift pipe by the time gas flow ceases, in the event that insufficient time is available for a gradual shut off of the primary stream, its sudden interruption will still leave within the lift pipe a quantity of solids so small that restarting of the lift with gas at the pressures and in the quantities normally available is assured.

What is claimed 1. In the operation of a gas lift forming the upflow path of a pressure balanced system through which granular material is continuously circulated, which system includes a down-flow path wherein said material gravitates as a compact non-turbulent mass enveloping, at the lower end thereof, the lower end of the lift path, the elevation of said material being effected by introducing the major portion of the lift gas into said mass in a confined stream discharging immediately adjacent the lift path inlet and the minor portion thereof into said mass at a point remote from said lift path inlet but in such proximity thereto as to provide the principal flow rate control for aid material, the method of shutting down said lift which comprises the sequential steps of: cutting off the flow of said minor portion of the lift gas, thereby reducing said flow rate to a relatively low value, cutting off the gravitational flow of said granular material at a point along said down-flow path, withdrawing from the upper end of said upfiow path at least a portion of the 'total granular material contained within said lift path and within the portion of said down-flow path below said point, and cutting ofi the flow of said major portion of the lift gas so as to interrupt the circulation of said granular material, whereby upon said interruption, a minimum of said granular material remains within said lift path to settle and form an accumulation at the lower end of said lift path.

2. A method as defined in claim 1 in which Said withdrawal of granular material from the upp end of said lift path is continued until substantially all of said total granular material has been withdrawn from the circulatory system.

WILLIAM W. WEINRICH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,347,358 Adams et a1 July 20, 1920 1,364,532 Von Porat 1 Jan. 4, 1921 1,390,974 Von Porat Sept. 13, 1921 1,498,630 Jensen June 24, 1924 1,549,285 Baker Aug. 11, 1925 2,493,911 Brandt Jan. 10, 1950 2,509,983 Morrow May 30, 1950 FOREIGN PATENTS Number Country Date 180,397 Great Britain May 11, 1922 268,667 Great Britain Apr. 7, 1927 

